One such valve is known, for example, from WO 98/48332. This valve is equipped with at least two valve steps of which two steps are coupled with each other variably and under mechanical or hydraulic action according to the principle of the hydraulic half bridge. Both variable valve steps are provided as inlet and as outlet valves of a pressure adjustment space and each has one closing body of defined geometry.
DE 44 26 152 A1 describes an electromagnetic pressure adjustment valve which can be used especially for the shifting pressure adjustment of automatic transmission of motor vehicles. The valve has one valve housing and one control slide actuatable by a magnet armature and connected therewith, the slide controlling the connections from a pressure medium inlet to a consumption terminal or to a reverse flow tank. The control slide is supported in a rear end and in a front bearing point in the valve housing and is prestressed via a setting spring.
Proportional pressure adjustment valves of the above mentioned kind are subject to a permanent further development relative to the functional properties, especially the optimizing of the hydraulic properties, the same as the increase in the reliability of the operation under differing conditions.
The problem on which this invention is based is to show a proportional pressure adjustment valve with improved hydraulic properties which, in particular, has a flow-rate optimized valve, which has substantially less drags especially in the range of lower temperatures, that is, under high viscosities of the hydraulic fluid.
On the basis of a proportional pressure adjustment of the above mentioned kind, this problem is solved with the features stated in claim 1. Advantageous developments are described in the sub-claims.